In the production of a microdevice such as a semiconductor device, a multi-charged beam exposure system for performing exposure to a pattern simultaneously with a plurality of charged beams without using any mask has been proposed.
In a multi-charged beam exposure apparatus using this system, the number of charged beams depends on the number of lenses in a multi-charged beam lens, and the number of lenses is a main factor which determines the throughput. Accordingly, how to improve the lens performance while downsizing the lens and increasing the density is one of the important factors for improving the performance of the multi-charged beam exposure apparatus.
Electron lenses are classified into electromagnetic and electrostatic types. The electrostatic electron lens does not require any coil core, or the like, and is simpler in structure and more advantageous to downsizing than the electromagnetic electron lens. Typical prior art concerning the electrostatic electron lens (electrostatic lens) will be described below.
A. D. Feinerman, et al. (J. Vac. Sci. Technol. A10(4), p. 611, 1992) disloses a method of anodically bonding a fiber and a V-groove formed by Si crystal anisotropic etching of an electrode fabricated by a micromechanical technique, thereby forming a three-dimensional structure from three electrodes serving as single electrostatic lenses. The Si film has a membrane frame, a membrane, and an aperture which is formed in the membrane and transmits and electron beam.
K. Y. Lee, et al. (J. Vac. Sci. Technol. B12(6), p. 3,245, 1994) discloses a structure obtained by bonding Si layers and Pyrex glass layers by using anodic bonding. This technique fabricates aligned microcolumn electron lenses.
Sasaki (J. Vac. Sci. Technol. 19, p. 963, 1981) discloses an arrangement in which three electrodes having lens aperture arrays are arranged into an Einzel lens. In an electrostatic lens having this arrangement, a voltage is generally applied to the central one of three electrodes, and the remaining two lenses are grounded, obtaining lens action.
However, a conventional electrostatic electron lens, which is formed by alternately stacking insulators and electrodes, has the following problems. More specifically, the electrodes serve as back electrodes for the insulators. Also, field electron emission at the triple point of the boundary between each insulator, vacuum region, and electrode may cause generation of electrons, or a secondary electron avalanche phenomenon may occur on the surface of any insulator. If this occurs, surface discharge is likely to occur on the surface of the insulator. This surface discharge may decrease the operating voltage or operational reliability of the electron lens.